This invention relates to an improved machine construction utilized in the formation of cast concrete members such as pavement curbing and the like. More specifically, the invention has specific utility with molding machines of the type disclosed in Heltzel U.S. Pat. No. 3,824,059 issued July 16, 1974. Such machine supports a plural cavity mold box through several operational stations including a cement or concrete charging station, a troweling and tamping station, and a discharge station. The mold box is thus successively moved through such stations on a supporting structure until the generally longitudinally orientated concrete members are hydraulically forced out of the mold in a zero slump partially set state for subsequent curing and use. The individual cavities of the mold are formed by a bottom member and upstanding sides. The top of the mold is open as are the ends.
In order to close the ends of the mold, sets of end plates are positioned thereat by means of hydraulic cylinders and in this way support the weight of concrete bearing thereagainst during the charging, tamping and setting operations. When the mold box is transferred to the discharge station, the front end plates are moved free of the front end of the mold cavities by the upward pivoting of a U-shaped frame to which they are mounted. Thereafter the second set of end plates in contact with the rear ends of the concrete members are hydraulically forced forward so as to eject the members from the mold. In many cases, however, due to the open top nature of the mold which results in a lesser amount of frictional contact between the mold and its member at the upper end thereof, upper portions of the freed front face of the members tend to distort or move forward prior to the time that the members are forced forwardly out of the mold by the rear hydraulic ejector. This tendency can result in distorted, i.e. forwardly canted front member faces. Inasmuch as these members are generally utilized in end-to-end abutting contact with each other, a member with an imperfect front end face results in a product that is either useless or must be used for a different and lower profit purpose. Obviously it would be desirable to prevent the above described frictional forces which take place in the mold from causing imperfect cast products.
The above prior art citation and discussion thereof constitutes applicants' Prior Art Statement and in that regard a copy of the Heltzel patent is enclosed with this application.